Jenna M. Lang edited Results and Discussion.md  over 8 years ago

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Phylogenetic analysis was performed using the full length (1482bp) 16S rDNA sequence from the genome assembly, not the shorter (1350bp) version from Sanger sequencing. The CoronadoT 16S rDNA sequence showed less than 95.5% identity to other _Porphyrobacter_ species and identity is even lower to other genera in the family. Given the low 16S rDNA identity to other members of the family, we did not perform DNA-DNA hybridization as this would have been uninformative \cite{Stackebrandt_1994} \cite{Tindall_2010} \cite{23591456}.  Phylogenetic trees built by varying the aligner, alignment and  tree-building algorithm, algorithms,  number of taxa for comparison, included,  and choice of outgroup demonstrated both that the current taxonomy of the family is in need of revision (as has been suggested by others, e.g. _e.g.,_  \cite{12656149} and \cite{25713040}) and that the placement of CoronadoT within the family is not stable. Because the Bayesian and Maximum Likelihood methods show a very similar topology, and are considered the most accurate methods for phylogenetic analysis (e.g. \cite{22456349}, \cite{8015439}, \cite{15590907}), we have shown those trees in Figure 2 and Figure 3. Both of these trees place CoronadoT within the _Porphyrobacter_ clade, though in the Bayesian tree there is a polytomy at the base of this clade. We note, as also shown recently by \cite{25713040}, that this clade is always polyphyletic with respect to _Erythromicrobium ramosum_ and often to _Erythrobacter litoralis_. In addition, CoronadoT is found on a long branch due to several changes that are unique to this strain, relative to the rest of the family. These changes are identical in both the assembly and the Sanger sequence and are all compatible with the secondary structure model of 16S (e.g. (_e.g.,_  changes in a stem nucleotide pair with the appropriate base). Based on this analysis, we chose to compare CoronadoT to the five other _Porphyrobacter_ species listed in Table 1. Analysis of the draft genome of strain CoronadoT was used to complement the physical characterizations typical of the family _Erythrobacteraceae_ and the genus _Porphyrobacter_. For example, CoronadoT does not contain any of the numerous genes involved in bacteriochlorophyll biosynthesis, rendering protein extraction/spectrophotometry unnecessary. Conversly, Conversely,  while no flagella were observed by TEM, this strain appears to possess the required genes making it likely that the flagella were lost in sample preparation or that their expression is condition-dependent. **Polar lipid, respitory lipoquinone, and fatty acid methyl esters** 

**Conclusions**  Strain CoronadoT clearly falls within the _Erythrobacteraceae_ family, based on both phylogenetic analysis and physical characteristics (notably fatty acid profile, carotenoid production, major respiratory quinone, and GC content). Using Bayesian and Maximum Likelihood trees, phylogenetic reconstruction,  the strain falls within a well-supported (but polyphyletic) _Porphyrobacter_ clade. In addition, CoronadoT shares a number of characteristics with _Porphyrobacter_, including the fatty acid profile, polar lipid composition, catalase activity, etc. The largest differences are the tolerance for growth at lower temperatures, elevated C16:0, and the lack of bacteriochlorophyll _a_ (for the latter of which we have proposed emending the genus description). These characteristics, in combination with the phylogenetic analysis, lead us to propose that Coronado T be classified as _Porphyrobacter mercurialis_ sp. nov. We are aware that a future in depth polyphasic comparative study and/or a genome sequencing based taxonomic revision of the entire family may merit a distinct genus for this this strain.